The present invention relates to wire rope and, more particularly, to plastic filled wire rope having spacer means between adjacent outer strands.
Plastic filled or encapsulated wire rope, such as disclosed in U.S. Pat. No. 3,824,777, has been demonstrated to have properties such as tensile strength, fatigue life and corrosion resistance superior to those of equal size bare wire rope. Such improved properties are derived from the separation of the core strand from the outer strands and the outer strands from each other by the thermoplastic material. Suitable thermoplastics include polypropylene, polyurethane, polyethylene, nylon, tetrafluroethylene or polyvinylchloride. Also useful are elastomers such as butyl or nitrile rubber. Such a coating reduces or eliminates such core to strand and strand to strand contact and abrasion when the rope is in service. Further, the coating traps any desired lubricant such as petrolatum, vegetable oils, asphaltic based materials and the like within the strands and resists the ingress of abrasive or corrosive elements into the rope.
However, it is desirable to achieve strand gap or interstice balance in the manufacture of such plastic encapsulated wire rope. Such gap balance insures the equal load sharing by the strands of the rope and also assures the spacing between strands is filled with plastic. One method of such gap control during rope manufacture is set forth in U.S. Pat. No. 3,824,777, wherein a strand gap controller die is utilized to equally separate rope strands during the injection of the plastic.
Another spacing control method is disclosed in U.K. Patent Application No. 2,090,305 A, wherein a preformed filler element of thermoplastic containing a linear reinforcing core is placed independently in the interstice. However, the presence of such independent thermoplastic element impedes or prohibits the introduction of a flowable thermoplastic into the wire rope.
Furthermore, in the course of use of plastic filled wire rope, there is a tendency for the outer portions of plastic at the exterior of the rope to separate from the inner portions of plastic near the core.
Therefore, it is an object of the present invention to provide an encapsulated wire rope having uniform strand gaps.
It is another object of the present invention to provide a plastic filled wire rope with reinforcements connecting inner and outer portions of the plastic fill.